Re: [PATCH V2 0/6] VA to numa node information

[Michal Hocko]

On Wed 12-09-18 13:23:58, Prakash Sangappa wrote:
> For analysis purpose it is useful to have numa node information
> corresponding mapped virtual address ranges of a process. Currently,
> the file /proc/<pid>/numa_maps provides list of numa nodes from where pages
> are allocated per VMA of a process. This is not useful if an user needs to
> determine which numa node the mapped pages are allocated from for a
> particular address range. It would have helped if the numa node information
> presented in /proc/<pid>/numa_maps was broken down by VA ranges showing the
> exact numa node from where the pages have been allocated.
> 
> The format of /proc/<pid>/numa_maps file content is dependent on
> /proc/<pid>/maps file content as mentioned in the manpage. i.e one line
> entry for every VMA corresponding to entries in /proc/<pids>/maps file.
> Therefore changing the output of /proc/<pid>/numa_maps may not be possible.
> 
> This patch set introduces the file /proc/<pid>/numa_vamaps which
> will provide proper break down of VA ranges by numa node id from where the
> mapped pages are allocated. For Address ranges not having any pages mapped,
> a '-' is printed instead of numa node id.
> 
> Includes support to lseek, allowing seeking to a specific process Virtual
> address(VA) starting from where the address range to numa node information
> can to be read from this file.
> 
> The new file /proc/<pid>/numa_vamaps will be governed by ptrace access
> mode PTRACE_MODE_READ_REALCREDS.
> 
> See following for previous discussion about this proposal
> 
> https://marc.info/?t=152524073400001&r=1&w=2

It would be really great to give a short summary of the previous
discussion. E.g. why do we need a proc interface in the first place when
we already have an API to query for the information you are proposing to
export [1]

[1] http://lkml.kernel.org/r/20180503085741.GD4535@xxxxxxxxxxxxxx
-- 
Michal Hocko
SUSE Labs